255
Operation Not Activated (Invalid Mode/Block Executing)
Fanuc · Alpha i series AC Servo Motor
What does 255 mean?
Operation cannot be activated because either an invalid mode is specified or a block execution is currently in progress. The system is either in an incompatible state or busy.
Common Causes
- Invalid mode specified for the requested operation.
- A block execution is currently in progress, preventing activation of a new operation.
Repair Steps & Checklist
Click steps to track your progress.
- 1
Check the current operating mode for compatibility.
- 2
Verify whether a block is currently being executed; wait for it to stop before activating a new operation.
Verified technical data. Last updated: March 2026
Related Faults
Source: Fanuc Alpha i series AC Servo Motor